The present methods, devices, and systems relate generally to the field of surgical robotics, and more particularly to the non-mechanical restriction of a manipulator (e.g., a robotic arm with multiple degrees of freedom) to movement of a tool by the manipulator along a single axis. An example of a procedure that can be carried out according to the present methods, devices, and systems is an automated biopsy. An example of a surgical robot that can be used in a procedure to which the present methods, devices, and systems relate is disclosed in U.S. Pat. No. 7,155,316 (the “'316 patent”), which is incorporated by reference.
In order to perform stereotactic procedures (e.g., take a needle or small tool and hit a target within a three dimensional space) it is advantageous to limit the extent to which the tool can deviate from its planned trajectory. Therefore, in order to use a robot to perform stereotactic procedures using a master-slave interface, it can be desirable to nullify any inputs to the master controllers in the X and Y coordinates thus restricting movement at the tool tip to the Z axis.
Current procedures using frame-based or frameless stereotactic tools create Z-lock conditions through mechanical limitations. The most common process for stereotactic procedures (frame-based) requires the fixture of a rigid head frame to the patient's head. This frame serves as a mechanical means of guiding stereotactic tools through pre-planned paths by mechanically limiting X and Y axis movement. Other frameless stereotactic tools that use mechanical arms or tool attachments execute stereotactic procedures by fixing the patient's head in space, positioning the mechanical arm in a pre-planned path position, and mechanically locking the degrees of freedom associated with the arm. The result is a mechanical Z-lock along a pre-planned path.
In both the frame-based and frameless stereotactic procedures, the pre-planned path is derived from an image taken hours before the procedure. However, the brain is not fixed within the cranial cavity and can shift as a result of damage, tumours, hydration, and body position changes. These relatively small brain shifts can be problematic in term of accuracy and pose a safety concern. As a result, post surgical images and other tools are used to ensure accurate and safe procedures with existing tools. Furthermore, in frame-based stereotactic procedures, attachment of a head frame to the patient's head is also required; this is both uncomfortable and time consuming.
Significant time is associated with pre-operative planning and post-surgical imaging. Moreover, frameless stereotaxy navigation systems require line of sight with the patient's head and the surgeon's tools. This can pose a problem for surgeons who need to be positioned by the head of the patient to navigate stereotactic tools to the target.